a) Field of the Invention
The present invention relates to a mobile communication method for communicating between a fixed station and a mobile station installed on a movable object.
b) Description of the Prior Art
The conventional method for debiting vehicles on toll roads and the like is an exclusively manual method in which an attendant manually receives a toll from each of the vehicles passing through the gate. Such a method is disadvantageous in that attendants must be employed, it causes a traffic jam depending on the number or flow of passing vehicles, and so on. To overcome such problems, many debiting systems have been developed which utilize various types of remote sensing techniques and radio communication techniques.
For example, Japanese Patent Laid-Open No. Hei 3-189798 disclose a system that uses ID plates, each of which is applied to a vehicle to be debited and stores the vehicle number and the balance of a contract or number of times the plate was accessed. An ID plate reader including an road antenna and a camera is located at a given point on the road (e.g., at a toll gate). The ID plate reader is adapted to carry out radio communication between the ID plate reader and the ID plate on a vehicle through the road antenna while capturing the license plate of that vehicle through the camera. The ID plate reader compares and checks the information of the vehicle number obtained through the radio communication with the information of the vehicle number obtained by image processing the captured image. If both sets of information coincide, the ID plate reader determines that the ID plate is properly used by the actual user.
However, such a system can properly function only when a single vehicle exists near the ID plate reader. Suppose that this system is applied to a single-lane road with a single ID plate reader being provided for the single road lane. If a plurality of motorbikes are moving on the single road lane side by side, a motorbike communicating with the ID plate reader is not necessarily coincident with a motorbike having its license plate captured by the camera of the ID plate reader. Even if any one of the motorbikes running side by side improperly uses the ID plate, therefore, the plate cannot be precisely detected.